1. Field
The present invention relates generally to apparatuses and methods for treating and preventing bleeding arising from the left atrial appendage using catheters having inflatable catheter balloons, at the pre-hemorrhage and post-hemorrhage stages.
2. Description of the Related Art
The left atrial appendage (LAA) is a small, conical, ear-shaped muscular pouch projecting from the upper anterior portion of the left atrium of the heart. Thus, the LAA lies within the pericardial cavity, and is an extension of the left atrium. The LAA functions as a decompression chamber during left ventricular systole and during periods when left atrial pressure is high. The LAA is also commonly known as the left auricular appendix, the auricular, or the left auricle. The left atrium receives oxygenated blood from the lungs by way of the pulmonary veins, and pumps the oxygenated blood into the left ventricle via the mitral valve.
Over the past 8 to 10 years, the LAA has become the target of several invasive procedures due to the high likelihood of embolic strokes arising from the LAA. During these procedures, bleeding arising from the LAA can occur. Additionally during these procedures, there can be tearing of the LAA. It is also anticipated that in the next few years, the number of invasive procedures involving the LAA is going to rise significantly. Invasive procedures of the heart targeting or involving the LAA is especially expected in patients who have atrial fibrillation (AF) and who may be at an increased risk of stroke arising from the LAA.
Bleeding arising from the LAA into the pericardial cavity is an emergent situation that requires immediate attention to stabilize the patient. If the bleeding is severe, cardiac tamponade can result and there may not be sufficient time to transfer the patient to an operating room for the proper care. Additionally, elderly patients are often not candidates for cardiac surgery due to advanced age and other comorbid issues. Thus, there is a need for novel percutaneous technologies and procedural techniques to treat hemorrhage arising from the LAA without subjecting the patient to cardiac surgery.
Additionally, there may also be a need to prevent bleeding arising from the LAA at the pre-hemorrhage stage, i.e. prior to the actual bleeding especially if the patient is to undergo a procedure involving the LAA, particularly where, as part of the procedure, the LAA may be intentionally pierced or perforated. The novel technology presented in this invention allows a puncture from the LAA onto the pericardial space or vice versa in a controlled setting without the development of hemorrhage into the pericardial cavity.
AF causes rapid randomized contractions of the atrial myocardium, resulting in an irregular and rapid ventricular rate and is currently, the most common type of cardiac arrhythmia. It affects more than 3 million patients in the United States, and this number is expected to climb to 16 million by 2050. AF is the most common cause of strokes arising from the heart due a blood clot forming in the heart.
Embolic stroke interrupts blood flow to the brain, thereby causing the affected brain cells to die. When brain cells die, the abilities controlled by the dying brain cells are compromised and eventually lost. In the United States, stroke is the third leading cause of death, killing approximately 160,000 Americans each year. Additionally, stroke is the leading cause of adult disability and there are currently over four million Americans living with the effects of stroke.
AF patients have a five-fold increased risk of an embolic stroke resulting primarily from thromboembolic events. In non-rheumatic AF patients, the stroke-causing thrombus originates almost exclusively from the LAA. Typically, the thrombus formed in the LAA break away from the LAA and accumulates in other blood vessels, thereby blocking blood flow in these blood vessels, and ultimately leading to an embolic stroke. Thus, the occlusion, stapling or ligation of the LAA is believed to be an effective stroke prevention technique. Several existing medical procedures aim to prevent the migration of thrombus from the LAA.
Commonly, rheumatic and non-rheumatic AF patients are administered warfarin, which is a therapeutic drug classified as an anticoagulant that helps prevent thromboembolism. An anticoagulant drug is a drug that suppresses, delays, or nullifies blood coagulation. Warfarin has the chemical name, 4-hydroxy-3-oxo-1-phenylbutyl-2H-benzopyran-2-one, and molecular formula, C19H16O4. However, a major drawback of warfarin is the difficulty of maintaining its therapeutic range, and thus, warfarin-administered patients require frequent monitoring and dose adjustments.
Alternatively, in patients intolerant of warfarin, occlusion of the LAA is believed to decrease the risk of an embolic stroke in non-valvular AF patients. Occlusion of the LAA is an obstruction or a closure of the LAA. By occluding the LAA, the thrombus formed in the LAA are unable to migrate to other blood vessels, thereby reducing the risks of thromboembolism and embolic stroke. Hence, the occlusion of the LAA is believed to be an effective stroke prevention strategy in non-valvular AF patients. Indeed, this concept of occluding the LAA as a stroke prevention strategy is being increasingly tested with implantable medical devices that occlude the LAA.
For example, the WATCHMAN device developed by Atritech Inc. (Plymouth, Minn.) is an implantable medical device designed to occlude the LAA in non-valvular AF patients. In particular, the WATCHMAN device is placed distal to the ostium of the LAA, thereby occluding the LAA. The occlusion of the LAA prevents the migration of the thrombus formed in the LAA, thereby reducing the risks of thromboembolism and embolic stroke. In the WATCHMAN device's clinical trial, PROTECT-AF trial, the results showed that in AF patients who were candidates for warfarin therapy, the closure of the LAA using the WATCHMAN device was associated with a reduction in hemorrhagic stroke risk as compared to warfarin therapy. Additionally, these results showed that all-cause stroke and all-cause mortality outcomes were non-inferior to warfarin.
However, a major drawback of the WATCHMAN device is the fixation of barbs or wires engaged in the walls of the LAA, thereby causing adverse events. As shown in the PROTECT-AF trial, a major adverse event is pericardial effusion, which is the abnormal accumulation of fluid in the pericardial cavity, which can negatively affect heart function. Another adverse event is the tearing of the walls of the LAA by the barb wires, thereby necessitating emergent surgery. The tearing of the LAA may lead to bleeding, which is an emergent situation that requires quick, decisive action to stop the bleeding and stabilize the patient.
Ligation of the LAA is yet another stroke prevention technique for patients intolerant of warfarin. In particular, the LAA is ligated with a suture using a percutaneous epicardial approach, resulting in a complete closure of the LAA. However, like the WATCHMAN device, a major drawback of this approach is the risks of bleeding and tears in the LAA.
Tears and bleeding arising from the LAA is particularly concerning for elderly patients because due to their advanced age, the walls of their LAA are fragile. As a result, elderly patients are more susceptible to tears and bleeding. Additionally, elderly patients are not candidates for cardiac surgery due to their advanced age and other significant comorbid issues.
In light of the foregoing, there is a compelling need for novel technologies and procedural techniques for treating and preventing bleeding arising from the LAA, at the pre-hemorrhage and post-hemorrhage stages, without subjecting the patient to cardiac surgery.